Featuring close to 200 bones, the fossil is about 80 percent complete.
The dinosaur roamed North America some 65 million years ago. Ranchers Kathy and Tom Wankel discovered the 38-foot-long fossil on federal land in Montana in 1988. It was excavated two years later.
After more than two decades at Montana's Museum of the Rockies, home to the largest dinosaur display in the world, the 7-ton fossil was packed into 16 crates for a cross-country road trip to Washington, D.C.
It was packed up carefully to avoid any damage in transit. "Just the wrong impact in the wrong place and it will shatter," explained the Smithsonian's Becky Kaczkowski as they packed the fossil. "We're making sure we minimize possibility for vibration the possibility for each mineral element touching another. So everything is strapped down and padded before it's strapped down."
The dinosaur will live -- so to speak -- at the Smithsonian for the next 50 years, on loan. It is the first T. Rex fossil to join the museum's dinosaur exhibit, which is more than 100 years old.
Visitors can get their first look over the next six months as curators unpack, examine and 3D scan the skeleton. It will take five years for the museum to overhaul its dinosaur exhibit and put the T. Rex on display.
The skeleton will be mounted upright for the first time, and will serve as the centerpiece of a $48 million gallery devoted to the history of life on Earth, slated to open in 2019.